Halifax is the first to add a new clause forcing customers to close their
existing account to qualify for its £100 cash offer.

Banks are quietly cracking down on savvy bank customers who flip between current accounts to take advantage of cash incentives.

The Telegraph understands that banks have been given a date of September 16 to start using a new seven-day switching guarantee that is expected to increase the number of people moving between banks.

Halifax, which offers £100 to new customers, last week introduced a rule that forces customers to close their existing current account to get the cash.

Previously, customers only had to transfer their direct debits to collect the money. This meant, in theory, you could still use your existing current account as the main hub for your salary and spending.

Other banks are set to make similar moves ahead the new seven-day switching rules. The scheme, designed by the banking industry, will automatically shut customers' existing accounts and move all payments to the new bank within seven working days. Customers will be compensated if anything goes awry.

A number of major High Street banks are preparing to launch new deals to attract customers ahead of this launch date. Several are also improving existing accounts and tightening criteria to guard against an exodus.

First Direct this week increased its switching offer to £125 but does not yet force customers to close their exiting account. Its minimum criteria are transferring at least two direct debits or standing orders and a salary or income of at least £1,000 a month within three months of opening the account.

David Black, head of banking at financial research firm Consumer Intelligence, said: "Banks want you using their services as your primary current account - they certainly don't want to pay you generous incentives if you aren't going to use it that way.

"Initially, banks tried to ensure this by stipulating a minimum monthly deposit from a salary or income. Increasingly, the terms have included a minimum number of direct debits or standing orders being transferred.

"Now some are asking you to use their own switching service and close your existing account to qualify for an offer or generous terms."

In May, Halifax came under fire for telling customers they would no longer receive the £5 a month reward on its current account unless they set up two monthly direct debits. Customers had previously needed to to pay in £1,000 a month to qualify for the cash perk. This was reduced to £750.

In response to the new account closing criteria, a spokesman for Halifax said: "The launch of seven-day switching will require customers to close their previous current account in order to utilise the service. "We are updating our processes in readiness for this and have introduced this requirement now."

Mark Hemingway, of the Payments Council, confirmed the new guarantee includes compulsory closure of the old account. Customers can opt out of the guarantee.